Measuring germanium trannies.

[jpm83]

I just bought a couple of AC127 trannies and I'm now measuring their leakage. My question is that how long I should let the measure drop  in my DMM, because I've been letting it drop for about 15 min. and it's still dropping?

Janne

[jpm83]

Never mind I got them measured. The the voltage dropping stopped it just took quite long.

[momo]

That happend to me too, I think if you manipulated the metal casing with your hands, the reading stabilizes when the temp does!, Im not sure on that, but I tried using tweezers and they seemed to stabilize faster....
Cheers

[jpm83]

Ok here are the results AC127no.1 hfe~87 leak 396µA no.2 hfe ~70 leak 313µA no.3 hfe~80 leak 371µA no.4 hfe~115 leak 548µA. AC116 tranny no.1 hfe~45 leak 13µA no.2 hfe~65 leak 18µA. AC132 hfe~237 leak 45µA.

Is that AC132 usable tranny in effect use? I was wondering because the leak was so low and hfe high.

Janne

[zeta55]

Don't know about the AC132, but the AC127 sounds great in this circuit. I also got a layout made up for it if there's a need.



/Krister

[jpm83]

Nice sounding stomper and great site you got (too bad my high school Swedish really sucks, and it wasn't so good even back then).
I was planning to do npn rangemaster from those AC127s, since I don't have a treble booster of any sort.

Janne

[Papa_lazerous]

a rangemaster is an ideal build if you are using a 127 use the one with hfe of 70, and make sure you get the bias sweet it is worth it

[kurtlives]

Sorry to go off topic

But what exactly is leakage and how does one meausre it?

[hellwood]

My question is that how long I should let the measure drop  in my DMM, because I've been letting it drop for about 15 min. and it's still dropping?Janne

i have checked hundreds using RG's technique and you will notice that the leakage/gain is almost proportional. as far as the gain goes, if you DONT TOUCH THE TRANSISTORS (use needlenose pliers) and you record your measurements relatively quickly(10 seconds), you will see that the gain results are pretty much the same as if you wait 15 min(+/- 3Hfe or so). ONLY if a transistor looks borderline leaky, i might sit there for a minute to see what happens.

[gaussmarkov]

Sorry to go off topic

But what exactly is leakage and how does one meausre it?

see Picking transistors for FF Clones

[hellwood]

Sorry to go off topic

But what exactly is leakage and how does one meausre it?

not off topic at all, look for RG's "the technology of the fuzz face" and you will find your answer.

[hellwood]

Ok here are the results AC127no.1 hfe~87 leak 396µA no.2 hfe ~70 leak 313µA no.3 hfe~80 leak 371µA no.4 hfe~115 leak 548µA. AC116 tranny no.1 hfe~45 leak 13µA no.2 hfe~65 leak 18µA. AC132 hfe~237 leak 45µA.

Is that AC132 usable tranny in effect use? I was wondering because the leak was so low and hfe high.

Janne

that is a wicked transistor for a shin-ei FY-2. if you dont want it, ill take it! ha-ha-ha!

[zeta55]

Nice sounding stomper and great site you got (too bad my high school Swedish really sucks, and it wasn't so good even back then).
I was planning to do npn rangemaster from those AC127s, since I don't have a treble booster of any sort.

Janne

Thanks.
Then I guess my school Finish sucks as bad as your school swedish
Good luck with those germaniums.

/Krister

[greigoroth]

Nice sounding stomper and great site you got (too bad my high school Swedish really sucks, and it wasn't so good even back then).
I was planning to do npn rangemaster from those AC127s, since I don't have a treble booster of any sort.

Janne

Hi Janne! http://lexin.nada.kth.se/sve-eng.html is an online dictionary which is pretty good, might help for all those millions of occasions when you need to understand a document in Swedish...

[kurtlives]

So I bread-boarded RG test circut.

But yeah really how long do I have to wait to find the leakage? What I am missing here?

Also why are AC125 so undesirable?

[hellwood]

But yeah really how long do I have to wait to find the leakage? What I am missing here?

Also why are AC125 so undesirable?

if you dont touch the transistor w/ your fingers and it reads 600, dont bother waiting around (its probably useless). if it reads 500 and slowly drops, set it aside as a last resort (it might be useless). if it reads <400 right off the bat, dont bother waiting around, just go ahead and calculate the gain(unless you are bored).

oh, i dont think that the AC125's are undesirable for any other reason than that they werent used for the vintage fuzz faces.

[kurtlives]

AC125 (I am using a 2.49K resistor)

Switch Off = 0.18V
0.18V / 2.49K = 0.072289uA

Switch On = 0.95V
0.95V - 0.072289uA = 0.877711
0.877711 x 100 = 87.7711 hFE
88 hFe

Is this the correct method?

[hellwood]

AC125 (I am using a 2.49K resistor)

Switch Off = 0.18V
0.18V / 2.49K = 0.072289uA

Switch On = 0.95V
0.95V - 0.072289uA = 0.877711
0.877711 x 100 = 87.7711 hFE
88 hFe

Is this the correct method?

according to RG..."Let's say the device really leaks 93uA, and has a gain of 110 - a prime specimen. What happens when we test? We chuck the thing in the socket, and read (93uA)*(2472) = .229V. Then we press the switch, and read 1.330V. To get the real gain, we subtract 0.229V from 1.330V and get 1.101V. The true gain is just 100 times the reading."

so in your case, (180uA)*(249) = .4482V Then we press the switch, and read 0.95V. To get the real gain, we subtract .4482V from 0.95V and get .5018. The true gain is just 100 times the reading."  50.18
someone please correct me if im wrong!

[Fuzzy-Train]

^ I believe that is incorrect...

Switch Off = 0.18V
0.18V / 2.49K = 0.072289uA

CORRECT

Switch On = 0.95V
0.95V - 0.072289uA = 0.877711
0.877711 x 100 = 87.7711 hFE
88 hFe

INCORRECT

Switch On = 0.95V
.18v - .95v = .77v
.77v * 100 = 77
True gain of 77Hfe w/.07ua

To get the true gain, subtract the 1st voltage reading, by the 2nd voltage reading, then multiply by 100.

[kurtlives]

^ I believe that is incorrect...

Switch Off = 0.18V
0.18V / 2.49K = 0.072289uA

CORRECT

Switch On = 0.95V
0.95V - 0.072289uA = 0.877711
0.877711 x 100 = 87.7711 hFE
88 hFe

INCORRECT

Switch On = 0.95V
.18v - .95v = .77v
.77v * 100 = 77
True gain of 77Hfe w/.07ua

To get the true gain, subtract the 1st voltage reading, by the 2nd voltage reading, then multiply by 100.

Alrighty thanks. I actually dug up of an old post of yours to do the calc. I guess you were wrong at one time too.

Is .07uA alright to use leakage wise?